Optical disk devices are used for the storage of computer prepared data and have value in their ability to store large quantities of data. The media for use in such devices is reactive to the intensity modulation of light such as may be produced by the rapid switching of a semi-conductor laser. In order to write data on optical media the laser power must be controlled at a relatively high power level in order that the media can be altered in accordance with the input data stream. In reading the data back the laser power level is controlled to a lower level so that the media is not altered by the laser beam, but the reflected light indicates the presence or absence of media alterations, i.e., digits of data corresponding to the input data stream.
Writable optical media is of two general types. Media which can be written only once and media which can be written, erased and written again. Write once media is permanently altered when write power levels are produced by the laser beam. Erasable media such as magneto-optic (MO) media is not permanently altered when data is written. In the MO media the magnetic orientation of the reactive material is selectively altered in the writing process and in the erasing process the magnetic orientation is reordered.
The American National Standards Institute (ANSI) has developed cartridges with standard dimensions for holding recording media. In that manner, the manufacturers of cartridges and the manufacturers of recording/play-back apparatus (drives) have the capability of developing their respective products for use with a variety of other manufacturer's products. A standard cartridge includes datum features, for example, locating holes that are designed to mate with datum features in a drive. For example, locating pins to accurately position the cartridge within the drive. Holding features in the cartridge such as notches and recesses are dimensioned relative to the datum features. After insertion of a cartridge into a drive the notches are typically used to hold the cartridge while it is loaded onto the locating pins and simultaneously loaded onto the drive spindle.
Optical media is placed within the standard cartridge and contains a standard media hub with a centering hole for accepting the spindle of a standard disk drive. The media hub also contains magnetic material for mating with a magnet located on the spindle of the disk drive. In that manner when the cartridge is inserted into the disk drive the optical media is placed on the spindle and located properly through the centering hole while the media hub is held to the drive spindle through magnetic action. When the spindle is caused to rotate the media rotates with the spindle.
In the standard design the media hub extends significantly below the surface of the optical media so that it may mate properly with the spindle of the disk drive. The inventors herein have noted that such a design limits the number of optical media which can be located within a given space. It is therefore, an object of the invention to design a media hub which is commensurate with the thickness of the media, that is not extending significantly below or above the surface of the optical disk and preferably of a dimension which is equal to or less than the dimension of the thickness of the optical disk.
It is a further object of the invention to provide a mini-library for use with a single optical disk drive. It is a still further object to provide such a mini-library with a maximum number of optical disks located within said library.